My Emotiva DAC for $300 in 2011 was modified with 5 $47 Sparkos regulators, high quality Panasonic power caps, film caps, etc. and a Synergistic Research purple fuse. The unit comes with a fully discrete audio board without Op-Amps. The result is $20K sounding DAC on the cheap. It also operates flawlessly, stand-by mode, digital close matched attenuation, nice heavy/quality remote (why is it that so much higher end gear have junky feeling plastic remotes) and light dimming display. Nothing missing in operation and sonically a window to the digital master whatever the engineer did. It is an equivalent but different sound than my analog set up. I’ve heard many under $20K DACs and very few expensive ($5K+) CD players. I don’t know if a CD player for less is as good as separates can be.
I'm sure that better DACs exist with more modern chips, clocks, etc. but basically, they need to sound musically involving and have great resolution, not leaving anything musically important out. I've achieved that on the cheap and I tried $9K DACs also superbly constructed/art works but lacking in musicality (electronics design failed due to a noise laden conversion algorithm).